Lubricant compositions

ABSTRACT

Lubricant compositions comprising: A. LUBRICATING OIL BASE B. REACTION PRODUCT OF ALKENYL SUCCINIMIDE AND DIALKYLDITHIOPHOSPHATE ACID ESTER 0.05-10 PERCENT C. TETRAALKYLTRITHIOPYROPHOSPHATE 0.001-2 PERCENT AND OPTIONALLY D. ALKENYL SUCCINIMIDE 0.05-10 PERCENT.

United States Patent [191 Breitigam et al.

[ LUBRICANT COMPOSITIONS [75] Inventors: Walter V. Breitigam, Wood River;

Bennett M. Henderson, Edwardsville, both of I11.

[73] Assignee: Shell Oil Company, New York, NY.

[22] Filed: Nov. 6, 1970 [21] Appl. No.1 87,593

[52] US. Cl 252/32.7 E, 252/51.5 A, 252/389, 252/400 [51] Int. Cl. Cl0m 1/48, ClOm 1/36 [58] Field of Search 252/32.7 E, 78, 51.5 A, 252/389, 400

[56] References Cited UNITED STATES PATENTS 12/1936 Salzberg et a1. 252/46.6 5/1965 Lowe et al. 252/466 Oct. 29, 1974 Primary Examiner-Daniel E. Wyman Assistant ExaminerI. Vaughn Attorney, Agent, or Firm-Henry C. Geller [57] ABSTRACT Lubricant compositions comprising: a. lubricating oil base b. reaction product of alkenyl succinimide and dialkyldithiophosphate acid ester 0.05-10 percent E. tliiiilliflirifiiiiipfibphosphate 0.001-2 percent and optionally Eifaik'ii i succinimide Obs-i0 seizes.

2 Claims, No Drawings 1 LUBRICANT COMPOSITIONS BACKGROUND OF THE INVENTION A great number of organic compounds have been described in the literature as extreme pressure (EP) additives. These materials are important in that they raise the load-carrying capabilities of the lubricant to reduce metal surface wear. Although there has been extensive research in this area, the theories explaining the mechanism of EP additives are mainly conjecture. Two of the most popular theories are:

l. the additives react with the lubricated metal surface at high temperatures to form easily-sheared films,

2. the additives hydrolyze to give a species which could be chemisorbed on a metal surfaceto provide the protective anti-wear film. These compounds can be generally classified as either ash-forming or ashless, the latter having wider applicability sincethis class of compounds can be used in ashless luboil formulations as well as in most other lubricant compositions.

One of the most suitable classes of EP additives known to the art are metal dithiophosphate salts such as zinc dialkyldithiophosphatesv While these salts are effective, they cannot be used in ashless lubricating compositions because they are ash forming; however, it has been discovered that using theashless succini' mide-type detergent additives in place of the previously used metal-containing materials aggravates the problem of controlling bearing corrosion and 'wear. The development of a new class of EP additives which could be used in a wide range of lubricant compositions is extremely desirable.

THE INVENTION This invention relates to lubricant oil compositions having improved extreme-pressure protection and bearing corrosion performance containingthe reaction product of an ashless succinimide and a thiophosphate acid ester combined in a suitable base stock'with a pyrophosphate derivative having the following general formula wherein each X is selected from the group consisting of oxygen and sulfur, and each R is a hydrocarbyl radical selected from the group consisting of C alkyl, C aryl and C alkaryl.

The ashless succinimide is preferably a polyalkenyl succinimide of a polyamine. as for example, polyisobutenyl succinimide of tetraethylenepentamine. However, a wide variety of succinic compounds of oilsoluble nitrogen compositions can be used provided they are hydrocarbon substituted, surface-active basic amines. The principle sources of the hydrocarbonsubstituent radical include high-molecular weight petroleum fractions and olefin polymers. particularly polymers of monoolefins having from'two to about carbon atoms. Especially useful are polymers of lmonoolefins such as ethylene, propene, l-butene, isobutene, l-hexene, l-octene, Z-methyI-I-heptene, 3- cyclohexyl- I -butene and 2-methyl-5-propyll -hexene. Polymers of medial olefins, that is, olefins in which the kylenepolyamines. A preferred source'of the amine group consists of alkylene polyamines conforming for the mostpart to the following formula:

where n is an integer,'preferably less than 10, A'is a hydrocarbon, hydrogen or amino radical and the alkylene radical is preferably less than C,,. Specific amines contemplated are exemplified by ethylene diamine, trieth ylenetetramine, propylene diamine, tetraethylene pentamine, di(trimethylen'e) triamine, l,'3-bis(2- aminoethylene) imidazoline' and 2-m'eth'yl-l-(2- aminobutyl) piperazine.

The thiophosphoric acids oracid compounds can be monoor dithio-having the following rcspectivegen'eral formulas:

wherein each R, is chosen from the group con'sistingof alkyl, aryl, alkaryl and aralkyl radicals. The alkyl radi-' cals include straight-chain, branched-chain, aliphatic and cycloaliphatic radicals. Examples of suitable radicals include methyl, ethyl, n-propyl, isopropyl,.isobutyl, secondary amyl, n-h'exyl, Z-ethylhexyl, n-octyl, nonyl, n-decyl, n-dodecyl, n-octadecyl, oleyl, cetyl, ceryl and the like, as'well as cyclohexyl, ethylcyclohexyl, tolyl, xylyl, naphthyl, benzyl, phenyl and the like.

Especially preferred are the alkyl dithiophosphoric acids, which can be conveniently prepared by reacting phosphorus pentasulfide and the appropriate alcohol,

for example, primary alkyl (C secondary alkyl (C,,-

to about C50) and branched alcohols such as 2-ethylhexyl, 3-ethyl-l-hexyl or 4 methy'l-l-pentyl andthe like. However, other conventional methods of preparing alkyl thiophosphate acids known to the art may be employed.

The pyrophosphate derivative is termed a mixed pyrophosphate. This refers to the fact that the-compounds contain both oxygen and sulfur and may vary in the sulfur-oxygen content with retention of the same ester group. These compounds can be prepared according to any method known in the art. See, for example, U'.S-. Pat. Nos. 3,297,797 and 2,063,629. Preferred are the oxydithioand trithiopyrophosphates;

ln general, the trithiopyrophosphates are prepared by one of two methods, depending on whether they are derived from alkyl or from aryl thionothiophosphoric acid.

Alkyl trithiopyrophosphates can be synthesized by reacting alkyl thionophosphoric acids with, for example. N.N '-dicyclohexylcarbodiimide.

The starting acid can be prepared by reacting a C alkyl alcohol or mercaptan with phosphorus pentasulfide. Examples of suitable alcohols and mercaptans are butyl alcohol. butyi mercaptan. and amyl. hexyl, heptyl. octyl. nonyl, decyl, undecyl alcohol or mercaptan. lauryl. stearyl. oleyl alcohol or mercaptan and the like. The nature of the alcohols or mercaptans used in synthesizing the thionophosphoric acids determines the nature of the alkyl groups of the trithiopyrophosphate subsequently formed.

Aryl and alkaryl trithiopyrophosphates can be conveniently prepared by reacting an aryl or alkaryl alcohol or mercaptan with phosphorus pentasulfide and then pyrolyzing the resultant thionothiophosphoric acid to the desired derivative.

A wide variety of aryl and alkaryl alcohols and mercaptans can be used in preparing suitable thionothiophosphoric acids. Examples of these are substituted and unsubstituted phenols. thiophenols, naphthols, thionaphthols and the like. C.. and C alkaryl alcohols or mercaptans having only one aromatic nucleus are especially suitable. Particularly advantageous alkaryl compounds are those having only one alkyl group attached directly to the aromatic nucleus, said alkyl group having from one to about 24 and preferably from about four to about 18 carbon atoms.

The reaction product of the succinimide and the thiophosphoric acid can be conveniently prepared. for example. by reacting the thiophosphoric acid and the basic amine at a temperature of about 80l20C. The thiophosphoric acid is then slowly added to the amine, stirred well. and heated to about 100C or more and stirred for approximately 2 hours. If higher heat is applied. the reaction time can be reduced to less than 2 hours. The resulting mixture is used in this form without further purification.

The novel combination of a thiophosphate acidsuccinimide reaction product and a thiopyrophosphate compound can be incorporated into a wide variety of lubricants. including synthetic oils. but are particularly advantageous when used in mineral lubricating oils. Mineral oils suitable for this invention can be obtained from paraffinic. naphthenic or mixed base blends and- /or mixtures thereof. For example. neutral oils having viscosities of from I to about 750 SSU at 100F may be employed. Neutral high viscosity index oils having viscosity indices (VI) of about 100 are preferred. Also suitable are oils having a viscosity index of at least 70 or suitable blends of lower viscosity index oils and viscosity improvers.

The reaction product and the pyrophosphates according to the invention can be added either separately or in combination to the lubricating oil in the amount of from 0.01 to about l0 /rw. A preferred composition contains from 0.05 to about 7(w.

Other additives can also be incorporated into the lubricating compositions of the present invention to add special properties to the compositions or to perform various functions. For example. any of the additives recognized in the art to perform a particular function. that is viscosity index improvers. antioxidants. antifoam agents. corrosion inhibitors. antirust agents and the like. can also be used.

The invention will be further illustrated by the following examples:

EXAMPLE I then filtered from any excess P 8 and reacted further as quickly as possible to avoid deterioration. No further purification steps were taken.

The di-Z-ethylhexyldithiophosphoric acid thus prepared was reacted with one equivalent of polyisobutenyl succinimide of tetraethylene pentamine as follows:

One mole (one equivalent weight) of di-2- ethylhexyldithiophosphoric acid was slowly added to an amount of the succinimide containing an equivalent amount of basic nitrogen and the mixture was stirred well while the temperature was maintained at C. After the addition, the mixture was heated to 100C and stirred for 2 hours. The resulting mixture was ready for use in this form, without further purification.

EXAMPLE ll This example describes a manner in which the tetra- 2-ethylhexyltrithiopyrophosphate derivative may be synthesized.

Di-2-ethylhexylthionophosphoric acid (0.] mole) was dissolved in anhydrous diethyl ether.

N.N'-dicyclohexylcarbodiimide (0.05 mole) was dissolved in anhydrous diethyl ether and added dropwise over 4 hours to the acid solution. The reaction was maintained at room temperature. After a short time, a white precipitate formed. The mixture was stirred for one hour at room temperature and to two hours at reflux temperature following the addition. The byproduct, N,N-dicyclohexylthiourea, MP. 1 80-l 8 1C, was then filtered. The product was recovered in -l00 percent of the theoretically possible amount, based on the acid. The solvent was removed from the remaining filtrate in vacuo.

EXAMPLE III In order to determine the load-carrying or extreme pressure capabilities of the additives of the invention, three compositions containing di-2- ethylhexyldithiophosphate-succinimide reaction product prepared according to Example I and identified as Compositions l. 2 and 3 were formulated as in Table 1. Composition 1 was not according to the invention. Test results are shown in Table 2.

TABLE I TABLE 3-Co'ntinued Component Composition "/1 \v Composition 4 7 I 3 viscosity at 25C 10 ppm Base Oil t t Hvl JON (viswsily approximately Oil soluble carbonated Ca petroleum sulfonatcs 6.6 m0 ssu ill IUOF) 99.0 97.7 96.

$53312; gggmgzg Composition 4 was then subjected to the Cam and acid-polyalkenylsuccinirnidc t0 Lifter Wear and Scuff Test using a 1967 425 cu. in. dis- :1 zf g a g f l 0 l 0 I U placement Oldsmobile engine, in which twice the norma] (production) valve spring pressure was applied. Tetra-Z-ethylhexyltrithiopyrophosphate" 1.3 1.3 Polyisohutenylsuccinimidgtf tetraethylenepcntamine (M T C approximately 2700) 1.5 Engine Prepared as in Example ll. V merage molecular weight l {j l 'p fl -b lz p j i mm own 011 t p! Test Duration: TABLE 2 Engine 5hr. (30 cycles) Coolant out. F: 95

Total l5hrs. Oil Sump F: I20 Four-Ball Wear Test" Composition Scar Diameter. mm '71 Seizure I O 436 Tested along with Composition 4 were two other oil 2 0.377 0 formulations that were identical with the exception that 3 0 they did not contain the additive combination accordymmblcs ing to the invention. These two oil formulations showed 2p It severe visible scuffing of cams and lifters at the conclufl T 5 sion of the test, while thecams and lifters lubricated Balls 2" diameter steel with Composition 4 had no visible scuffing, only 6 X 10' inches of measured wear. "-ltl kg load I Th F B ll W 'd l d EXAMPLE W e oura ear test 18 W1 e y accepte as a repeatable screening test for EP lubricants Scar diamer: so sgie fj e gtg fpgg ogiiigg g zg ters less than about 0.42 mm with no seizure indicate h T 4 f l d d thatalubricant has EP properties such that satisfactory YE e was Ormu ate teste performance in automotive cam and lifter follower sets e e is probable. The wide differences in scar diameter and TABLE 4 the lack of seizure are clearly indicative of the im- 40 proved extreme pressure properties of the inventive composition 5 compositions. v 7

I W HVl l00N (viscosity approximately 100 SSU at l 00F) 46.5 EXAMPLE IV HVl 250N (viscosity approximately 262 SSU at l00F) 38.] To further illustrate the extreme pressure properties 1 28x3285: lgg llgiiyl g g gzggyff 0' 4 6 of the comppslluons of the mventlon! 13%, of q' Polyisobutenyl succinimidc of tctraethylene ethylhexyltrithiopyrophosphate and l%w of the d1-2- pentamine (M -approximately 2700) 1.7 ethylhexyldithiophosphate acid-succimmide reaction as :mf ftlg bz zi fi product were evaluated in the formulated lubricant phosphoricucid-pulyulkens'l-succinimide or llt th 'len-- *ntam' 1.0 composltlon lcomposmon 4) shown m Table 3' lso oiit ilpl tentixifietraelliitxyethanol 0.2 TABLE 3 Carbonated calcium sulfonates 611 Silicone polymer. l2.500 cs viscosity at 25C l0 ppm Composi ion 4 according to the invention H WON (5mm approximate. The effectiveness of these materials as oxidation inloll SSL' ill I00Ft 46.5 hibitors was demonstrated by evaluating Composition H HUN ("5mm "ppmimmh. No. 5 in the CLR L-38 (FTM 791a Method 3405) test. 262 SSL' ill low) 38.l This test subjects the oil to 285F (bulk temperature) Cowhnm ,mmhLMMHPYIMM to demonstrate the oxidation stability (as indicated by laur l ntethacrvlate stearyl corrosive weight loss of the copperlead connecting rod 3 59355) a vv t 4 6 bearing) of a lubricant. Composition No. 5 produced less than 50 mg weight loss in 40 hours. This perform- Pnli sn uw y c j J ance is similar to that expected of a formulation in '{,1'f, WWW m which 1.4%w zinc dialkyldithiophosphate was substi- 7 tuted for 1.3%w trithiopyrophosphate. If neither comlsooct)lphenoxytetraetltox} ethanol 0. pound were included catastrophicweight loss Silicone polymer 12.500 cs (greater than 1000 mg) would be expected.

Other disclosed compositions not exemplified in the above examples give equivalent, although not identical, results. The additives disclosed herein are suitable for use in multipurpose hydraulic fluids as well as in a wide variety of both ashless and ash-forming lubricating oils.

We claim as our invention:

1. An ashless lubricant composition comprising a major amount of a mineral lubricating oil which is a neutral hydrocarbon oil with a viscosity index of at least 70 and A. from about 0.05 to 10 percent by weight ofa reaction product of polyisobutenyl succinimide of 8 tetraethylenepentamine wherein the succinimide has an average molecular weight between from 0.05 to 10 percent by weight of a polyisobutenyl succinimide of tetraethylenepentamine. 

1. AN ASHLESS LUBRICANT COMPOSITION COMPRISING A MAJOR AMOUNT OF A MINERAL LUBRICATING OIL WHICH IS A NEUTRAL HYDROCARBON OIL WITH A VISCOSITY INDEX OF AT LEAST 70 AND A. FROM ABOUT 0.05 TO 10 PERCENT BY WEIGHT OF A REACTION PRODUCT OF POLYISOBUTENYL SUCCINIMIDE OF TETRAETHYLENEPENTAMINE WHEREIN THE SUCCINIMIDE HAS AN AVERAGE MOLECULAR WEIGHT BETWEEN 400-3,000 AND DI-2-ETHYLHEYLDITHIOPHOSPHORIC ACID, SAID REACTION BEING CARRIED OUT BY HEATING AN EQUIVALENT WEIGHT OF EACH EACTANT AT A TEMPERATURE OF ABOUT 80*-120*C AND UTILIZING SAID PRODUCT WITHOUT FURTHER PURIFICATION AND B. FROM ABOUT 0.001 TO 2 PERCENT BY WEIGHT OF TETRA 2ETHYLHEXYLTRIHIOPYROPHOSPHATE.
 2. The composition of claim 1 having additionally from 0.05 to 10 percent by weight of a polyisobutenyl succinimide of tetraethylenepentamine. 